A nation mourns

While investigators search for evidence at the crime scene and gather more details on the killer's claimed allegiance to militant group Islamic State, a shocked nation mourns the victims of the massacre at the Pulse nightclub in Orlando, Florida.

Fifty, including 29-year-old gunman Omar Mateen, were killed at the nightclub, which catered to the LGBT community. It was the deadliest mass shooting in modern U.S. history.